Independent rotor blades in both axial flow turbines and radial flow compressors or turbines are subject to the danger of vibration. During operation, the individual blades of such turbomachines execute natural vibrations which depend on the type of vibration to which they are subjected, such as tangential bending, axial bending or torsion.
Known methods of vibration damping include connecting together several blades to form a group, fully enclosed fastening by means of shrouds at the blade tips or solid connection elements on the blade airfoils in their radially outer region and, finally, tangential or zig-zag-shaped threading of damping wires or brazing in connecting wires.
Most of the methods become inappropriate if it is necessary to undertake vibration damping measures in the case of the integral turbines of exhaust gas turbochargers which today operate at very high peripheral speeds. Up till now, these one-piece rotors could only be provided with cast-on connecting elements. The latter procedure is, however, extremely difficult, and manufacture is consequently expensive.